High resolution cathode ray tube shadow-mask

ABSTRACT

An improved aperture mask is provided for use in a two beam shadow mask type of color cathode ray tube. The mask is utilized in the formation and subsequent operation of a patterned screen including a repetitive array of two phosphor areas. The multitude of apertures defined by the interstitial webbing of the mask member are arrayed in a plurality of parallel rows having given directional orientations. Any three mutually adjacent apertures in any two adjacent parallel rows are oriented to form an isosceles right triangular relationship. The resultant screen associated therewith exhibits enhanced resolution and brightness.

Umted States Patent 1191 [111 3,777,202

Say Dec. 4, 1973 [54] giggg gkgg CATHODE RAY TUBE FOREIGN PATENTS OR APPLICATIONS 1,163,495 9/1969 Great Britain 313/85 S [75] Inventor: Donald L. Say, Waterloo, NY. [73] Assignee: GTE Sylvania Incorporated, Seneca Examineri'i- Saaibach F ll N Y Att0rneyNorman J. OMalley et a1.

[22] Filed: July 19, 1972 57 ABSTRACT 21 Appl. No.: 273,158 1 An improved aperture mask is provided for use in a Related Apphcatlon Data two beam shadow mask type of color cathode ray 1 Division of 153,695, June 16, i971 tube The mask is utilized in the formation and subseuent o eration of a patterned screen including a re- 1 P petitive array of two phosphor areas. The multitude of [52] 11.8. C1. 313/85 S apertures defined by the interstitial webbing of the [51] Int. Cl. H01J 29/50 mask member are arrayed in a plurality of parallel [58] Fleld of Search 313/85 S rows having given directional orientations Any three mutually adjacent apertures in any two adjacent paral- [561 References Cted lel rows are oriented to form an isosceles right triangu- UNITED STATES PATENTS lar relationship. The resultant screen associated there- 2,s57,551 10/1958 Hansen 313/85 s with exhibits enhanced resolution and brightness- 2,728,008 12/1955 Bumside.... 313/85 S 3,003,873 10/1961 Zworykin 313/85 s 3 Chums, 3 Drawmg 8"? PATENTED SHEET 1 OF 2 PRIOR ART 1 HIGH RESOLUTION CATI-IODE RAYTUBE SHADOW-MASK CROSS REFERENCE TO RELATED APPLICATION This application is a divisional application ofSer. No. 153,695, filed June 16, 1971, which is assigned to the assignee of the present invention, and now US. Pat. No. 3,720,854 filed '3/13/73.

BACKGROUND OF THE INVENTION Thisjnvention relates to cathode ray tubes and more particularly to color cathode ray .tubesemploying shad- :factors in a, vivid luminous manner. In some applications a limited number of simultaneous color or hue differences are adequate for the presentation of an evaluation display. Forthis type .of system, a socalled two color cathode ray tube is appropriate. Such a tube nor- :mally utilizes two electron beams and a patterned screen formed of a repetitive array of two separate phosphor areas from which the additive aspects-of a composite hue may also be obtained. .A conventional shadow .mask tri-color tube can be adapted for this usage by eliminating one of the three electron guns and the associated phosphor component in the screen pat-' tern. However, when such is done, the blank areas in the screen are detractive factors affecting both the resolution and the brightness of the display. Thus, it has been found that the aperture arrangement in the conventional tri-color shadow mask tube cannot be effectively utilized to produce an efficient two-phosphor screen ,of the quality required for the display application.

OBJECTS AND SUMMARY OF. THE INVENTION It is an object of the-invention to reduce the aforementioned disadvantages. and to providev an improved shadow mask for a cathode ray tube having an aperture array appropriate for effecting an efficient twophosphor patterned screen exhibiting enhanced resolution and improved brightness. v

Another object is to provide an improved apertured shadow mask and a two-phosphor screened panel combination for use in a' two beam cathode ray tube.

The foregoing objects are achieved in one aspect of the invention wherein an improved shadow mask, for use in a cathode ray tube employing two electron beams and a patterned screen including a repetitive array of two phosphor areas, exhibits a discrete aperture arrangement. The foraminuous mask. member comprises a multitude of apertures which are defined by the interstitial webbing and arrayed in a substantially uniform pattern. effecting a plurality of parallel BRIEF DESCRIPTION-OF THE DRAWINGS FIG. 1 is anenlarged fragmentary plan-view illustrating a prior art relationship-of the mask apertures with the associated patternedscreen;

FIG. 2 is a partial perspective view showing the DESCRIPTION :OF THE PREFERRED EMBODIMENT For a betterunderstanding .of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to thefollowing specification and appended claims in connection with the aforedescribed drawings.

The descriptive phraseology two-color cathode ray tube as used in this specification refers to a tube employing two separate electron beams and a patterned cathodoluminescent screen comprising a repetitive array of two phosphorareas. Each of the phosphor areas is made up of one or more phosphor materials which, when exicted, emits a distinctive hue. Simultaneous excitation of both phosphor areas produces a third color formed as an additive composite hue. By way of example, green G" and red R luminescent dots will be described herein.

With reference to the drawings, there is shown in FIG. 1 anenlarged fragmentary plan view of a prior art aperture mask 11 and associated patterned screen 13 relationship as viewed from the source of electron beams within the tube. The foraminous shadow mask member 11 has therein a multitude of apertures l5-defined by the opaque interstitial webbing l7 and pres- .ents an aperture array as employed in a conventional tri-color or tri-dot colorcathode ray tube. The aperture array is directly related to the X and Y axes of the mask therefore B o. In considering adjacent parallel rows X-X' and BE, the adjacent apertureshaving centers 0, m,. and n form an isosceles tiangle omn.

' While related triangles lmo and om'n have a common side on and equal sides am and mn, they are otherwise respectively dissimilar: d) 60, while d) 120;

B F 6.03. whereas. s HI 39".; an Si??? 0 i Shorter than side on." In view of the unlike triangular relationships, the linear spacing t between apertures in the rows oriented in the Y-Y' direction are equal to the linear spacings between apertures in the rows oriented in the diagonal W-W and J-J directions, while the aperture spacings w in the X-X directional orientation are greater. In similar manner the color repeat spacings v between adjacent parallel rows of apertures in the Y axial direction are greater than the row spacings s in the X direction.

The two-color screen 13 formed on the glass substrate or receiving panel 19 and operationally associated with the prior art mask 11 is comprised of pairs of G and R phosphor areas. Since the third phosphor color area has been eliminated from this twocolor screen 13, the panel area 21 usually covered by the third phosphor is free of phosphor material in the screen pattern 13 shown. Thus, it is clearly evident that high resolution and brightness cannot be expected from the aforedescribed prior art screen 13 wherein over one-third of the panel screen area is free of phosphor material.

In reference to FIG. 2, a partial perspective view denotes portions of a cathode ray tube 25 enclosed by a fragmentarily shown envelope 27 wherein the viewing panel 19 has a two-color screen pattern 29 in the form of repetitive pairs of contrasting phosphor areas disposed in rows thereon. A metallic foraminous shadow mask 31 is spatially positioned relative to the screen 29 being directly associated with the formation and subsequent operation of the patterned screen. In usage, the apertured shadow mask 31 and screened viewing panel 19 are considered as a combination assembly 33, and as such are conventionally spatially affixed by means not shown. Additionally, predeterminately positioned within the envelope 27 is a source of electrons 37 oriented in a manner to direct two separate electron beams 39 and 41 toward the apertured shadow mask 31 and the related screen 29. As shown, the electron beams 39 and 41 converge at the mask 31 passing through an aperture 43 therein and thence selectively impinging and exciting separate phosphor areas of the screen 29 to provide a luminescent display.

In greater detail, reference is made to FIGS. 2 and 3 wherein the shadow mask 31 comprises a multitude of apertures 43 defined by the opaque interstitial webbing 45. The apertures are arrayed in a substantially uniform pattern being adjacently related in a manner to effect a plurality 'of rows which, in turn, define a plurality of linear directional relationships such as, C-C, Y-Y, L-L and K-K. The rows of a given directional orientation are substantially parallel, as for example: X-X and A-A', Y-Y and C-C, L-L and M-M', and K-K' and N-N. The rows X-X and Y-Y' define the respective X and Y axial directions in the shadow mask member 31.

Any three mutually adjacent apertures in any two adjacent parallel rows are substantially oriented in an isosceles right triangular relationship. For example, three mutually adjacent apertures, having centers of a, b, and respectively, are oriented in adjacent-parallel rows Y-Y' and C-C', in O-O' and L-L', and in N-N' and K-K. The resultant triangle abc includes a right angle a and an acute angle 0 of 45. Since the acute angles are complements of each other, the remaining acute angle 8 is also 45, and therefore the respective sides ab and cb are equal; consequently, the spacings p and q between adjacent diagonal rows are also equal. A similar isosceles right triangle cbd is formed of the three mutually adjacent apertures 43 having centers c, b, and d which are oriented in adjacent parallel rows X-X' and A-A','in L-L' and M-M', and in N-N and K-K. The two isosceles right triangles abc and cbd are equal since they have a common side cb andangular equalities, i.e. a a, 6 276' and 6=-8'. The hypotenuse ac of triangle abc is definitive of the Y axial direction in the mask, and the counterpart hypotenuse cd of triangle cbd is definitive of the X axial direction. In each of the respective triangles abc and cbd, the sides forming the right angle, for example, in abc, sides ab and cb forming the right angle a, define the diagonal directions N-N and L-L in the mask, each diagonal being associated with the respective X and Y axes in substantially 45 angular relationships. The described diagonal relationships diametrically divide each of the apertures 43 into four substantially equal 90 segments 49, 50, 51 and 52.

The linear spacings h and f between the individual mask apertures in the rows directionally associated with both the X and Y axes are substantially equal since the hypotenusal sides ac and cd of similar triangles abc and cbd are of equal lengths. The spacings e and g between adjacent parallel rows, of apertures, such as X-X', A-A and Y-Y' and C-C', in both the X and Y directions are equal in view of the equalities of dimensions bj and bj, each being normal to the mid-points of the hypotenusal sides ac and cd of the similar triangles abc and cbd. Therefore, the spacings e and 3 between adjacent parallel rows of apertures, which are in effect color repeat dimensions, associated with both the X and Y axial directions are advantageously equal; and in addition, these spacings e and g are equal to substantially one-half the respective linear spacings f and h between the apertures in the respective rows in view of the equalities the aforementioned triangular dimensions whereof, aj =jc cj =j'd.

The improved shadow mask 31 of the invention has more apertures per area or greater transparency than does the described prior art mask 11, and therefore the improved mask 31 affords higher resolution and enhanced brightness by permitting the passage of a greater density of exciting electrons. In considering the greater transparency of the improved mask 31, attention is drawn to FIG. 3 wherein the aforedescribed triangular area abd is referenced. For purposes of example, the following values are ascribed:

Aperture dia. k 0.0090 inch ac orf 0.0250 inch jb or g 0.0125 inch color repeat spacing for both X and Y axes (same asj' b or e) Improved Mask Transparency 1r(0.004=5) area of aperture 2 =20 7 Area of triangle abc 0.025 0.0125 0 Improved Mask color repetitions per inch' vertically and horizontally l m repeats 1n.

Prior art mask transparency:

Prior art mask color repetitions per inch vertically l/0.0l08 92.5 repeats/in. Prior art mask color repetitions per inch horizontally U001 88 53.2 repeats/in. Thus, on the basis of comparative dimensions, the mask 31 of the invention provides improved transparency and resolution for two-color tube utilization.

With reference to FIGS. 2 and 3, the two-color screen pattern 29 comprises a repetitive array of two phosphor areas or dots which are substantially equally adjacent to one another, being disposed in accordance with the aperture array of the mask 31. The two phosphor areas, in this instance, are conventional cathodoluminescent materials such as those that emit green G or red R luminous hues when electron excited. The two phosphor areas, G, R are alternately and adjacently disposed in substantially linear parallel rows in both horizontal and vertical X and Y, directional relationships in the screen 29. In the X axis directional relationship, the phosphor rows are oriented in a manner that the linear diametrical axes of the phosphor dots Z-Z' and that of the apertures X-X are substantially coincidental. There are no large vacant areas 21 in the screen as are evidenced in the prior art screen 13 in FIG. 1.

As shown, the phosphor areas G, R have a diameter iwhich is greater than the diameter k of the related aperture. Such diametrical relationship is not intended to be limiting, as the dots may also be of a size equal to or smaller than the apertures and still be in keeping with the concept of the invention. There may be instances when it is desirous to form a screen pattern array wherein the individual phosphor areas are disposed in an equidistant spaced-apart relationship. Such alteration of the pattern spacing could necessitate a proportional modification of the triangular dimensions between the apertures in the mask, however, the dimensional relationships therebetween would remain substantially constant in keeping with the teaching of the invention. 9

In FIG. 2, the source of electrons 37 is an electron gun structure assembled in a manner to provide and direct two separate electron beams 39, 41 to the maskscreen portion 33 of the tube 25. The individual beams are controlled to selectively excite a respective one of the two phosphor areas G, R in a predetermined sequence to provide a luminescent display in the twocolor screen 29. As indicated, the directional line of scan 8-8 of the two beams 39, 41 is substantially parallel with the X-X axial orientation of the mask apertures 43 and such is preferred; but there may be occasions when the electron beams are oriented to scan the mask 31 and associated screen 29 in a modified manner. lt has been found that the line of scan SS' can be shifted clockwise or counter-clockwise with reference to the X-X' of the mask, but such deviation should not exceed a substantially 45 angular relationship with the X-X axis of the mask.

Thus, there is provided cathode ray tube shadow mask having a discrete aperture array for effecting an efficient two-phosphor patterned screen for use in a two-beam tube whereof the resultant luminescent image exhibits enhanced resolution and improved brightness.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without'departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A multi-opening shadow mask for use in a color cathode ray tube wherein the apertures of said mask are utilized in the formation and subsequent operation of a discretely patterned cathodoluminescent screen including a repetitive array of two phosphor areas oriented substantially equally adjacent to one another in accordance with the aperture pattern of said mask, said mask comprising:

a metallic foraminous member wherein the multitude of apertures defined by the interstitial webbing are arrayed in a substantially uniform pattern, said apertures being adjacently related in a manner to effect a plurality of rows defining a plurality of linear directional relationships, said rows of a given directional orientation being substantially parallel, any three of said mutually adjacent apertures in any two adjacent parallel rows being substantially oriented in an isosceles right triangular relationship.

2. An apertured shadow mask according to claim 1 wherein said isosceles right triangular relationships are oriented in a manner that the hypotenusal sides thereof define the respect've X and Y axial directions in said foraminous member, and wherein the sides forming the right angle relationship of said isosceles right triangle define the diagonal directions in saId foraminous member being associated with said respective X and Y axes in substantially 45 degree angular relationships, said diagonalsdiametrically dividing each of said apertures into four substantially equal segments.

3. An apertured shadow mask according to claim 2 wherein the linear spacings between the mask apertures in the rows directionally associated with both the X and Y axes are substantially equal, and wherein the spacings between adjacent p'arallel rows of apertures in both the X and Y axes are equal, and wherein the spacings between adjacent parallel rows of apertures associated with both the X and Y axes are equal to substan' tially one-half the linear spacing between the apertures in said rows directionally associated with both of said UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 77,2 2 Dated December 4, 1973 Inventor(s) Donald y 3 Q It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column Line' 8, "filed" should read issued Column Line 52, "on" should rad om Line 63, 6' should re ad Column 3 Line 63, 270' should read 9 I Column 3 Column Lino 2, I should read Signed and sojal-ed this 11th day of June 1971;; v

(SEAL) Attest:

Eowm MJ'LETCHERJ'R. I c. MARSHALL mum Atteating Officer Commissioner of Patents 

1. A multi-opening shadow mask for use in a color cathode ray tube wherein the apertures of said mask are utilized in the formation and subsequent operation of a discretely patterned cathodoluminescent screen including a repetitive array of two phosphor areas oriented substantially equally adjacent to one another in accordance with the aperture pattern of said mask, said mask comprising: a metallic foraminous member wherein the multitude of apertures defined by the interstitial webbing are arrayed in a substantially uniform pattern, said apertures being adjacently related in a manner to effect a plurality of rows defining a plurality of linear directional relationships, said rows of a given directional orientation being substantially parallel, any three of said mutually adjacent apertures in any two adjacent parallel rows being substantially oriented in an isosceles right triangular relationship.
 2. An apertured shadow mask according to claim 1 wherein said isosceles right triangular relationships are oriented in a manner that the hypotenusal sides thereof define the respective X and Y axial directions in said foraminous member, and wherein the sides forming the right angle relationship of said isosceles right triangle define the diagonal directions in saId foraminous member being associated with said respective X and Y axes in substantially 45 degree angular relationships, said diagonals diametrically dividing each of said apertures into four substantially equal segments.
 3. An apertured shadow mask according to claim 2 wherein the linear spacings between the mask apertures in the rows directionally associated with both the X and Y axes are substantially equal, and wherein the spacings between adjacent parallel rows of apertures in both the X and Y axes are equal, and wherein the spacings between adjacent paRallel rows of apertures associated with both the X and Y axes are equal to substantially one-half the linear spacing between the apertures in said rows directionally associated with both of said axes. 